[Intel-gfx] [PATCH] drm/i915/gen11: use ffs for minconfig slice/subslice

[Surendrakumar Upadhyay, TejaskumarX]

> -----Original Message-----
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Sent: 11 June 2021 23:36
> To: Surendrakumar Upadhyay, TejaskumarX
> <tejaskumarx.surendrakumar.upadhyay at intel.com>
> Cc: intel-gfx at lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH] drm/i915/gen11: use ffs for minconfig
> slice/subslice
> 
> On Fri, Jun 11, 2021 at 08:04:09PM +0530, Tejas Upadhyay wrote:
> > w/a on gen11 platforms not working as expected and causing more harm
> > on the RC6 flow. Because of subslice steering disturbance w/a read is
> > failing. By using ffs we can default steering of slice/sublice to
> > minconfig hence w/a will pass and any warns will go away.
> >
> > Fixes: fb899dd8ea9c ("drm/i915: Apply Wa_1406680159:icl,ehl as an
> > engine workaround")
> > Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> > Cc: Matt Roper <matthew.d.roper at intel.com>
> > Signed-off-by: Tejas Upadhyay
> > <tejaskumarx.surendrakumar.upadhyay at intel.com>
> > ---
> >  drivers/gpu/drm/i915/gt/intel_workarounds.c | 14 +++++++++++---
> >  drivers/gpu/drm/i915/intel_pm.c             | 10 +++++++---
> >  2 files changed, 18 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > index b62d1e31a645..68b14141088a 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > @@ -991,13 +991,21 @@ wa_init_mcr(struct drm_i915_private *i915,
> struct i915_wa_list *wal)
> >  		l3_en = ~0;
> >  	}
> >
> > -	slice = fls(sseu->slice_mask) - 1;
> > -	subslice = fls(l3_en & intel_sseu_get_subslices(sseu, slice));
> > +	if (GRAPHICS_VER(i915) == 11) {
> > +		slice = ffs(sseu->slice_mask) - 1;
> > +		subslice = ffs(l3_en & intel_sseu_get_subslices(sseu, slice));
> > +	} else {
> > +		slice = fls(sseu->slice_mask) - 1;
> > +		subslice = fls(l3_en & intel_sseu_get_subslices(sseu, slice));
> > +	}
> >  	if (!subslice) {
> >  		drm_warn(&i915->drm,
> >  			 "No common index found between subslice mask %x
> and L3 bank mask %x!\n",
> >  			 intel_sseu_get_subslices(sseu, slice), l3_en);
> > -		subslice = fls(l3_en);
> > +		if (GRAPHICS_VER(i915) == 11)
> > +			subslice = ffs(l3_en);
> > +		else
> > +			subslice = fls(l3_en);
> >  		drm_WARN_ON(&i915->drm, !subslice);
> >  	}
> >  	subslice--;
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c
> > b/drivers/gpu/drm/i915/intel_pm.c index 45fefa0ed160..d1352ec3546a
> > 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -4049,9 +4049,13 @@ skl_ddb_entry_for_slices(struct
> drm_i915_private *dev_priv, u8 slice_mask,
> >  		ddb->end = 0;
> >  		return;
> >  	}
> > -
> > -	ddb->start = (ffs(slice_mask) - 1) * slice_size;
> > -	ddb->end = fls(slice_mask) * slice_size;
> > +	if (GRAPHICS_VER(dev_priv) == 11) {
> > +		ddb->start = (fls(slice_mask) - 1) * slice_size;
> > +		ddb->end = ffs(slice_mask) * slice_size;
> > +	} else {
> > +		ddb->start = (ffs(slice_mask) - 1) * slice_size;
> > +		ddb->end = fls(slice_mask) * slice_size;
> > +	}
> 
> This code has nothing to do with GT slices.

Without this change we are observing "gem_exec_suspend (basic-s0) Starting subtest: basic-S0" test hangs and crash eventually. Thus change identified and added. Would you please help reviewing?

Also I am seeing ICL igt at kms_frontbuffer_tracking@fbc-suspend is seeing workaround(0x9524) lost warning after this patch while EHL and JSL are working fine. does someone has insight why that should be
 the case? 

Thanks,
Tejas
> 
> >
> >  	WARN_ON(ddb->start >= ddb->end);
> >  	WARN_ON(ddb->end > INTEL_INFO(dev_priv)->dbuf.size);
> > --
> > 2.31.1
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> --
> Ville Syrjälä
> Intel